The present invention relates to a gas turbine engine, and more particularly to an arcuate vane platform segment having a substantially flat surface over which a rotational turbine vane swings.
The core engine of a gas turbine engine typically includes a multistage axial compressor which provides compressed air to a combustor wherein it is mixed with fuel and ignited for generating hot combustion gas which flows downstream through a high pressure turbine nozzle and in turn through one or more stages of turbine rotor blades. The high pressure turbine blades are joined to a rotor disk which is joined to the compressor by a corresponding drive shaft, with the turbine blades extracting energy for powering the compressor during operation. In a two spool engine, a second shaft joins a fan upstream of the compressor to a low pressure turbine disposed downstream from the high pressure turbine.
Typical turbine nozzles, such as high pressure and low pressure turbine nozzles, have fixed vane configurations and fixed turbine nozzle throat areas. Variable cycle engines are being developed to maximize performance and efficiency over subsonic and supersonic flight conditions. Some engines provide variability in compressor vanes by mounting each vane on a radial spindle and collectively rotating each row of compressor vanes using an annular unison ring attached to corresponding lever arms joined to each of the spindles. Each compressor vane rotates about a radial axis, with suitable hub and tip clearances which permit rotation of the vanes.
Although it would be desirable to obtain variable flow through turbine nozzles by adjusting the throat areas thereof, previous attempts thereat have proved difficult because of the turbine nozzles severe operating environment. Adjustable turbine nozzle vanes may reduce the structural integrity and durability of the nozzle segments in view of the increased degree of freedom therebetween. Furthermore, it may be difficult to seal the movable portion of the airfoil because the flowpath wall is cylindrical, conical, or otherwise curved in nature.